Device for straightening crankshafts



Jan. 22, 1963 J. F. LEIGHTER i 3,074,463

DEVICE FOR STRAIGHTENING CRANKSHAFTS Filed March 13, 1961 3 {i715} #63 navrcn non srnhrdn'rnrtmo errants Eames F. Leighter, Independence, Mo. (1423 Kansas Ave., Kansas City, Mo.) Filed Mar. 13, 1961, Ser. No. 95,185 2 Ciainrs. (Cl. 153-32) This invention relates to a device for straightening the grankshafts of engines and the like when they become ent.

For example, rotary lawnmowers are usually driven by a small engine which is mounted as a complete assembly on the ibase of the mower and has a depending crankshaft on which the blade is directly mounted, consequently the crankshaft is often bent when the blade strikes an immovable object. Ordinarily this requires Clismantling of the engine to remove the crankshaft so that it can be straightened. lt is obvious that much time and labor can be saved by straightening the crankshaft while mounted in the engine, since the bend usually occurs on the outboard end of the shaft, but this usually results in damage to the engine because all of the force required to straighten the shaft is also applied to the outboard bearing and case of the engine.

The present invention is to provide a device for straightening bent crankshafts of engines without dismantling the engine and without damaging the bearing and engine case.

@ther objects of the invention are to indicate the amount that the crankshaft is bent, the sides of the shaft to which the straightening and resisting forces are to be applied, and to indicate when the shaft is in true alignment.

In carrying out the invention, the engine is removed from the mower as a complete unit, and the base thereof` is bolted to the straightening device, so that the bent end of the shaft projects through a bracket of the device, for contact by a pair of opposing jack screws, one of which is operated to support the shaft against the bending force of the other, thereby relieving the straightening force rom the engine.

In accomplishing the above objects of the invention, I have provided improved structure, the preferred form of which is illustrated in the accompanying drawings, wherein:

iG. l is a face view of a crankshaft straightening device constructed in accordance with the present invention and showing an engine supported thereby and with the crankshaft in position to be straightened.

HG. 2 is a side elevational view, partially in section, to better illustrate the adapter sleeve and jack screws for respectively supporting and straightening the shaft.

FIG. 3 is a fragmentary perspective view showing the shaft straightening elements of the device.

FG. 4 is a perspective view of an adapter sleeve, part of the sleeve being broken away to better illustrate the screw for eecting removal thereof when the shaft is in straight condition.

Referring more in detail to the drawings:

1 designates a shaft straightening device constructed in accordance with the present invention, and which includes a horizontal base 2 adapted for attachment to a work bench or the like, not shown. One end of the base 2 has an upstanding transverse flange 3 for attaching an upright d by fastening devices such as bolts 5. The upright d is of generally channel shape and has a web portion 6 of a width and height to accommodate the base flange 7 of an engine S having a bent crankshaft 9. The flanges 16 and 12. of the upright 4 preferably extend outwardly from the base 2 to provide the desired rigidity of the web 6. The web e has an opening 12 therein of large diameter, so that the opposite face of the web proafrit vides a dat annular seating face 13 for the base of the engine and to accommodate openings 14 for securing the engine base thereto by suitable fastening devices such as bolts 15.

Fixed to the flanged side of the web 6 and extending transversely across the opening is a bracket '16 having spaced apart side plates 17 and 18. The side plates are of like construction, and each comprises a midportion 19 and laterally diverging arm portions 20 and 21 that extend across the opening on opposite sides of the center thereof. The arm portions Ztl and 21 are rigidly attached to the face of the web, as, for example, by Welds 22. The midportions of the arms 2%? and 21 are parallel and are interconnected at the diverging points of thearms by blocks 23 and 2d to accommodate the bent end of the crankshaft freely therebetween. The midportons of the arms, as well as the blocks 23 and 2d, are preferably of a width corresponding to the projection of the crankshaft, as shown in FIG. 2.

The upper block 23 has an internally threaded opening Z5 near the outer edge thereof, while the lower block 24 has an internally threaded opening 27 near the rear or opposite edge thereof. The openings are also located in a vertical plane extending through the axis of the crankshaft, that is, the opening 26 is located directly over the shaft near the outer end thereof and the opening 27 is below the shaft near the outboard bearing portion of the engine casing. Threaded into the openings 26 and 27 are the threaded Shanks 28 and 2@ of jack screws 30 and 31, each having head portions 32 and 33 adapted t0 be engaged by a wrench or the like for turning the shanks of the jack screws into and out of the openings. The jack screws are thus located in spaced apart relation and in the true vertical axial plane of the crankshaft 9.

in order to protect the crankshaft from being marred by the jack screws, the shaft is protected by a sleeve-like adapter 3d having an open end 3S of a diameter to accommodate the shaft and a closed opposite end 36, to mount an abutment screw 37. The closed end is provided with an internally threaded opening 33 for accommodating the externally threaded shank 39 of the screw 37. The screw 37 has a head dit adapted to be engaged by a suitable wrench, not shown. The adapter has a bore 41 extending inwardly of the open end of a diameter to closely engage the end of the crankshaft when the adapter is appiied to the projecting end of the shaft.

The device also is provided with a pointer 42, pivotally mounted on the lower block 24 by means of a screw 43. The pointer includes an angularly extending arm portion te having one end terminating in a point 4S to move over a scale 45 that is attached to the web portion yof the upright, as indicated in FIGS. l and 2. rfhe opposite end of the pointer terminates in an angularly extending feeler d'7 adapted to engage the periphery of the adapter sleeve, as shown in FIG. l, to indicate the amount of bend in the crankshaft and to locate the bend in the plane of the jack screws. The scale de has a zero marking 48 at which the pointer represents the straight position of the shaft, and graduations 49 and Si? extending above and below the zero mark d, respectively, to indicate not only the amount of the bend, but the deflection to be imparted in the shaft that is necessary to bring the shaft into a permanently set straightened condition.

In using the device constructed and assembled as described for straightening the bent crankshaft `of a lawnmower engine, the blade is removed from the crankshaft and the engine in its entirety is removed from the mower. An adapter sleeve 35i is applied to the end of the crankshaft to avoid damage to the crank shaft during straightening thereof as later described. The engine is then secured to the seating face i3 of the upright support by means of the bolts 15, so that the bent end 9 of the crankl v shaft, with the adapter sleeve thereon, extends through the opening 12 and through the opening between the upper and lower blocks 23 and 24 of the bracket 16, as shown in FiGS. 1 and 2. In this position, the feeler E47 is in engagement with the periphery of the adapter sleeve on the crankshaft. The crankshaft is then turned until the pointer 45' reaches its lowest position from the zero niarking 48. At this point, the bend in the shaft is in plane with the Shanks of the jack screws 3@ and 31. rI'he jack screw 31 is then turned in the threaded opening 27 by engaging a suitable wrench with the head 33 thereof, to bring the end of the jack screw into Contact with the bearing sleeve, to form a support for the crankshaft in opposition to the jack screw 3i). In this wa the force of the jack screw 3@ is removed Afrom the crankcase and bearing of the engine.

With the shaft suitably backed by the jack screw 31, the jack screw 3i) is turned into the opening 26 by applying a wrench to the head 32 thereof. The jack screw is rotated to force theV crankshaft into straight condition. During this manipulation of the jack screw 3), the deection of the crank shaft is indicated by the point i5 of the pointer 42, since the adapter sleeve bears upon the feeler arm 47 of the pointer. Usually the jack screw Sil needs to urge the shaft beyond its straight position as indicated by the pointer in registry with the zero marking 43 of the scale, so that when the pressure is released they v shaft returns to straight condition and remains in straight condition.

The shaft is then checked through a full 360 rotation upon slacking oi both of the jack screws. If the point 5 of the pointer remains on zero position throughout the full rotation of the crankshaft, the bent end of the crankshaft has been restored to straight condition. However, if there is any deviation from the zero position, the jack screws are again manipulated until there is no deviation of the point 'i5 from the zero position.

When the shaft is in straight condition, the engine is removed from the straightening device by disconnecting the bolts 15. The screw 37 is then rotated against the end of the shaft to loosen the adapter for ready removal from the shaft. The engine is remounted on the mower and the cutter blade is reattached to the depending end of the crankshaft.

From the foregoing` it is obvious that I have provided a crankshaft straightening device which supports the shaft during bending thereof, so as to relieve the straightening force from the bearing portion of the crankcase. it is also obvious that I have provided-a crankshaft straightening device which is of simple construction and which rnay be sold at a iow cost to the sinall engine and Vmower repair shops.

. While I have particularly illustrated and described the invention for use in straightening the crankshafts of small engines used as the power for lawninowers, it is obviousV that the device is adaptable to straightening the crankshaft of any small engine, regardless of the use thereof.

zi/'hat l clairs and desire to secure by Letters Patent is;

1. A device for straightening the end of a crankshaft that projects from the case of a small engine or the like, including a base, an upright on the Abase having any annular se on one side for seating the case of the engine and ing opening therethrough for projection of the bent end of the shaft, means for securing the case of the engine to said seat, spaced apart plates having parallel midportions and diverging arrn portions spanning the opening in said upright and engaging the side of the yupright opposite to said seat, rneans for rigidly securing the ends of theV arrns to the upright, upper and lower transverse blocks connecting said midportions of the plates in spaced apart relation to provide for projection of the engine shaft therebetween, a backing screw carried by the lower lblock near the projection of the shaft from the case for backing said shaft, and a jack screw carried by the upper block for engaging the opposite side of the bent end of the shaft near the end thereof for straightening said bent end of the shaft over against saidbacking screw.

2. A device for straightening the bent end of a crankshaft that projects from the case of a small engine or the like, as described in claim 1, and which includes a lever pivoted on the lower of said yblocks and having a feeler portion on said pivoted end for engaging said end of the shaft and having a pointer on the other end, and a scale xed to the uprightY for indicating the position of the pointer.

References Cited in the le of this patent UNTED STATES PATENTS 

1. A DEVICE FOR STRAIGHTENING THE END OF A CRANKSHAFT THAT PROJECTS FROM THE CASE OF A SMALL ENGINE OR THE LIKE, INCLUDING A BASE, AN UPRIGHT ON THE BASE HAVING AN ANNULAR SEAT ON ONE SIDE FOR SEATING THE CASE OF THE ENGINE AND HAVING AN OPENING THERETHROUGH FOR PROJECTION OF THE BENT END OF THE SHAFT, MEANS FOR SECURING THE CASE OF THE ENGINE TO SAID SEAT, SPACED APART PLATES HAVING PARALLEL MIDPORTIONS AND DIVERGING ARM PORTIONS SPANNING THE OPENING IN SAID UPRIGHT AND ENGAGING THE SIDE OF THE UPRIGHT OPPOSITE TO SAID SEAT, MEANS FOR RIGIDLY SECURING THE ENDS OF THE ARMS TO THE UPRIGHT, UPPER AND LOWER TRANSVERSE BLOCKS CONNECTING SAID MIDPORTIONS OF THE PLATES IN SPACED APART RELATION TO PROVIDE FOR PROJECTION OF THE ENGINE SHAFT THEREBETWEEN, A BACKING SCREW CARRIED BY THE LOWER BLOCK NEAR THE PROJECTION OF THE SHAFT FROM THE CASE FOR BACKING SAID SHAFT, AND A JACK SCREW CARRIED BY THE UPPER BLOCK FOR ENGAGING THE OPPOSITE SIDE OF THE BENT END OF THE SHAFT NEAR THE END THEREOF FOR STRAIGHTENING SAID BENT END OF THE SHAFT OVER AGAINST SAID BACKING SCREW. 